diff --git a/src/ImageSharp/Formats/Heif/Av1/Av1Math.cs b/src/ImageSharp/Formats/Heif/Av1/Av1Math.cs
index 9e4831f01a..59da84eeea 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Av1Math.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Av1Math.cs
@@ -144,6 +144,9 @@ internal static class Av1Math
     internal static int Clamp(int value, int low, int high)
         => value < low ? low : (value > high ? high : value);
 
+    internal static long Clamp(long value, long low, long high)
+        => value < low ? low : (value > high ? high : value);
+
     internal static int DivideLog2Floor(int value, int n)
         => value >> n;
 
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Av1ForwardTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Av1ForwardTransformer.cs
index 3528842677..de33eae8f1 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Av1ForwardTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Av1ForwardTransformer.cs
@@ -36,12 +36,11 @@ internal class Av1ForwardTransformer
     internal static void Transform2d(Span<short> input, Span<int> coefficients, uint stride, Av1TransformType transformType, Av1TransformSize transformSize, int bitDepth)
     {
         Av1Transform2dFlipConfiguration config = new(transformType, transformSize);
-        ref int buffer = ref TemporaryCoefficientsBuffer[0];
         IAv1Forward1dTransformer? columnTransformer = GetTransformer(config.TransformFunctionTypeColumn);
         IAv1Forward1dTransformer? rowTransformer = GetTransformer(config.TransformFunctionTypeRow);
         if (columnTransformer != null && rowTransformer != null)
         {
-            Transform2dCore(columnTransformer, rowTransformer, ref input[0], stride, ref coefficients[0], config, ref buffer, bitDepth);
+            Transform2dCore(columnTransformer, rowTransformer, input, stride, coefficients, config, TemporaryCoefficientsBuffer, bitDepth);
         }
         else
         {
@@ -55,7 +54,7 @@ internal class Av1ForwardTransformer
     /// <summary>
     /// SVT: av1_tranform_two_d_core_c
     /// </summary>
-    private static void Transform2dCore<TColumn, TRow>(TColumn transformFunctionColumn, TRow transformFunctionRow, ref short input, uint inputStride, ref int output, Av1Transform2dFlipConfiguration config, ref int buf, int bitDepth)
+    private static void Transform2dCore<TColumn, TRow>(TColumn transformFunctionColumn, TRow transformFunctionRow, Span<short> input, uint inputStride, Span<int> output, Av1Transform2dFlipConfiguration config, Span<int> buf, int bitDepth)
             where TColumn : IAv1Forward1dTransformer
             where TRow : IAv1Forward1dTransformer
     {
@@ -87,8 +86,13 @@ internal class Av1ForwardTransformer
         // ASSERT(txfm_func_col != NULL);
         // ASSERT(txfm_func_row != NULL);
         // use output buffer as temp buffer
-        ref int tempIn = ref output;
-        ref int tempOut = ref Unsafe.Add(ref output, transformRowCount);
+        Span<int> tempInSpan = output[..transformRowCount];
+        Span<int> tempOutSpan = output.Slice(transformRowCount, transformRowCount);
+        ref int tempIn = ref tempInSpan[0];
+        ref int tempOut = ref tempOutSpan[0];
+        ref short inputRef = ref input[0];
+        ref int outputRef = ref output[0];
+        ref int bufRef = ref buf[0];
 
         // Columns
         for (c = 0; c < transformColumnCount; ++c)
@@ -98,7 +102,7 @@ internal class Av1ForwardTransformer
                 uint t = (uint)c;
                 for (r = 0; r < transformRowCount; ++r)
                 {
-                    Unsafe.Add(ref tempIn, r) = Unsafe.Add(ref input, t);
+                    Unsafe.Add(ref tempIn, r) = Unsafe.Add(ref inputRef, t);
                     t += inputStride;
                 }
             }
@@ -108,20 +112,20 @@ internal class Av1ForwardTransformer
                 for (r = 0; r < transformRowCount; ++r)
                 {
                     // Flip upside down
-                    Unsafe.Add(ref tempIn, r) = Unsafe.Add(ref input, t);
+                    Unsafe.Add(ref tempIn, r) = Unsafe.Add(ref inputRef, t);
                     t -= inputStride;
                 }
             }
 
             RoundShiftArray(ref tempIn, transformRowCount, -shift[0]); // NM svt_av1_round_shift_array_c
-            transformFunctionColumn.Transform(ref tempIn, ref tempOut, cosBitColumn, stageRangeColumn);
+            transformFunctionColumn.Transform(tempInSpan, tempOutSpan, cosBitColumn, stageRangeColumn);
             RoundShiftArray(ref tempOut, transformRowCount, -shift[1]); // NM svt_av1_round_shift_array_c
             if (!config.FlipLeftToRight)
             {
                 int t = c;
                 for (r = 0; r < transformRowCount; ++r)
                 {
-                    Unsafe.Add(ref buf, t) = Unsafe.Add(ref tempOut, r);
+                    Unsafe.Add(ref bufRef, t) = Unsafe.Add(ref tempOut, r);
                     t += transformColumnCount;
                 }
             }
@@ -131,7 +135,7 @@ internal class Av1ForwardTransformer
                 for (r = 0; r < transformRowCount; ++r)
                 {
                     // flip from left to right
-                    Unsafe.Add(ref buf, t) = Unsafe.Add(ref tempOut, r);
+                    Unsafe.Add(ref bufRef, t) = Unsafe.Add(ref tempOut, r);
                     t += transformColumnCount;
                 }
             }
@@ -141,11 +145,11 @@ internal class Av1ForwardTransformer
         for (r = 0; r < transformRowCount; ++r)
         {
             transformFunctionRow.Transform(
-                ref Unsafe.Add(ref buf, r * transformColumnCount),
-                ref Unsafe.Add(ref output, r * transformColumnCount),
+                buf.Slice(r * transformColumnCount, transformColumnCount),
+                output.Slice(r * transformColumnCount, transformColumnCount),
                 cosBitRow,
                 stageRangeRow);
-            RoundShiftArray(ref Unsafe.Add(ref output, r * transformColumnCount), transformColumnCount, -shift[2]);
+            RoundShiftArray(ref Unsafe.Add(ref outputRef, r * transformColumnCount), transformColumnCount, -shift[2]);
 
             if (Math.Abs(rectangleType) == 1)
             {
@@ -154,7 +158,7 @@ internal class Av1ForwardTransformer
                 int t = r * transformColumnCount;
                 for (c = 0; c < transformColumnCount; ++c)
                 {
-                    ref int current = ref Unsafe.Add(ref output, t);
+                    ref int current = ref Unsafe.Add(ref outputRef, t);
                     current = Av1Math.RoundShift((long)current * NewSqrt, NewSqrtBitCount);
                     t++;
                 }
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst16Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst16Forward1dTransformer.cs
index b3c343538c..927e333e83 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst16Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst16Forward1dTransformer.cs
@@ -7,8 +7,12 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Transform.Forward;
 
 internal class Av1Adst16Forward1dTransformer : IAv1Forward1dTransformer
 {
-    public void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange)
-        => TransformScalar(ref input, ref output, cosBit);
+    public void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange)
+    {
+        Guard.MustBeSizedAtLeast(input, 16, nameof(input));
+        Guard.MustBeSizedAtLeast(output, 16, nameof(output));
+        TransformScalar(ref input[0], ref output[0], cosBit);
+    }
 
     private static void TransformScalar(ref int input, ref int output, int cosBit)
     {
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst32Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst32Forward1dTransformer.cs
index 9f707ae639..ba907e3a04 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst32Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst32Forward1dTransformer.cs
@@ -7,8 +7,12 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Transform.Forward;
 
 internal class Av1Adst32Forward1dTransformer : IAv1Forward1dTransformer
 {
-    public void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange)
-        => TransformScalar(ref input, ref output, cosBit);
+    public void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange)
+    {
+        Guard.MustBeSizedAtLeast(input, 32, nameof(input));
+        Guard.MustBeSizedAtLeast(output, 32, nameof(output));
+        TransformScalar(ref input[0], ref output[0], cosBit);
+    }
 
     private static void TransformScalar(ref int input, ref int outputRef, int cosBit)
     {
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst4Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst4Forward1dTransformer.cs
index 2b4952873a..38b11dfbfb 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst4Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst4Forward1dTransformer.cs
@@ -7,8 +7,12 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Transform.Forward;
 
 internal class Av1Adst4Forward1dTransformer : IAv1Forward1dTransformer
 {
-    public void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange)
-        => TransformScalar(ref input, ref output, cosBit);
+    public void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange)
+    {
+        Guard.MustBeSizedAtLeast(input, 4, nameof(input));
+        Guard.MustBeSizedAtLeast(output, 4, nameof(output));
+        TransformScalar(ref input[0], ref output[0], cosBit);
+    }
 
     private static void TransformScalar(ref int input, ref int output, int cosBit)
     {
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst8Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst8Forward1dTransformer.cs
index 8019df88c5..701973fc4c 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst8Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Adst8Forward1dTransformer.cs
@@ -7,8 +7,12 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Transform.Forward;
 
 internal class Av1Adst8Forward1dTransformer : IAv1Forward1dTransformer
 {
-    public void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange)
-        => TransformScalar(ref input, ref output, cosBit);
+    public void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange)
+    {
+        Guard.MustBeSizedAtLeast(input, 8, nameof(input));
+        Guard.MustBeSizedAtLeast(output, 8, nameof(output));
+        TransformScalar(ref input[0], ref output[0], cosBit);
+    }
 
     private static void TransformScalar(ref int input, ref int output, int cosBit)
     {
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct16Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct16Forward1dTransformer.cs
index 1173c56de7..ea515aad5d 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct16Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct16Forward1dTransformer.cs
@@ -7,8 +7,12 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Transform.Forward;
 
 internal class Av1Dct16Forward1dTransformer : IAv1Forward1dTransformer
 {
-    public void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange)
-        => TransformScalar(ref input, ref output, cosBit);
+    public void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange)
+    {
+        Guard.MustBeSizedAtLeast(input, 16, nameof(input));
+        Guard.MustBeSizedAtLeast(output, 16, nameof(output));
+        TransformScalar(ref input[0], ref output[0], cosBit);
+    }
 
     private static void TransformScalar(ref int input, ref int output, int cosBit)
     {
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct32Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct32Forward1dTransformer.cs
index c0068072d3..2b49035f29 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct32Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct32Forward1dTransformer.cs
@@ -7,8 +7,12 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Transform.Forward;
 
 internal class Av1Dct32Forward1dTransformer : IAv1Forward1dTransformer
 {
-    public void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange)
-        => TransformScalar(ref input, ref output, cosBit);
+    public void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange)
+    {
+        Guard.MustBeSizedAtLeast(input, 32, nameof(input));
+        Guard.MustBeSizedAtLeast(output, 32, nameof(output));
+        TransformScalar(ref input[0], ref output[0], cosBit);
+    }
 
     private static void TransformScalar(ref int input, ref int output, int cosBit)
     {
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct4Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct4Forward1dTransformer.cs
index 41a5234594..d43e2535c0 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct4Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct4Forward1dTransformer.cs
@@ -7,8 +7,12 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Transform.Forward;
 
 internal class Av1Dct4Forward1dTransformer : IAv1Forward1dTransformer
 {
-    public void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange)
-        => TransformScalar(ref input, ref output, cosBit);
+    public void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange)
+    {
+        Guard.MustBeSizedAtLeast(input, 4, nameof(input));
+        Guard.MustBeSizedAtLeast(output, 4, nameof(output));
+        TransformScalar(ref input[0], ref output[0], cosBit);
+    }
 
     private static void TransformScalar(ref int input, ref int output, int cosBit)
     {
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct64Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct64Forward1dTransformer.cs
index c9149f2973..57b59cc488 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct64Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct64Forward1dTransformer.cs
@@ -7,10 +7,14 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Transform.Forward;
 
 internal class Av1Dct64Forward1dTransformer : IAv1Forward1dTransformer
 {
-    public void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange)
-        => TransforScalar(ref input, ref output, cosBit);
+    public void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange)
+    {
+        Guard.MustBeSizedAtLeast(input, 64, nameof(input));
+        Guard.MustBeSizedAtLeast(output, 64, nameof(output));
+        TransformScalar(ref input[0], ref output[0], cosBit);
+    }
 
-    private static void TransforScalar(ref int input, ref int output, int cosBit)
+    private static void TransformScalar(ref int input, ref int output, int cosBit)
     {
         Span<int> temp0 = stackalloc int[64];
         Span<int> temp1 = stackalloc int[64];
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct8Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct8Forward1dTransformer.cs
index e8e449ac45..923227e57f 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct8Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Dct8Forward1dTransformer.cs
@@ -7,8 +7,12 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Transform.Forward;
 
 internal class Av1Dct8Forward1dTransformer : IAv1Forward1dTransformer
 {
-    public void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange)
-        => TransformScalar(ref input, ref output, cosBit);
+    public void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange)
+    {
+        Guard.MustBeSizedAtLeast(input, 8, nameof(input));
+        Guard.MustBeSizedAtLeast(output, 8, nameof(output));
+        TransformScalar(ref input[0], ref output[0], cosBit);
+    }
 
     private static void TransformScalar(ref int input, ref int output, int cosBit)
     {
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1DctDct4Forward2dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1DctDct4Forward2dTransformer.cs
index b0115d440f..9442618d20 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1DctDct4Forward2dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1DctDct4Forward2dTransformer.cs
@@ -12,7 +12,7 @@ internal class Av1DctDct4Forward2dTransformer : Av1Forward2dTransformerBase
     private readonly Av1Dct4Forward1dTransformer transformer = new();
     private readonly int[] temp = new int[Av1Constants.MaxTransformSize * Av1Constants.MaxTransformSize];
 
-    public void Transform(ref short input, ref int output, int cosBit, int columnNumber)
+    public void Transform(Span<short> input, Span<int> output, int cosBit, int columnNumber)
     {
         /*if (Vector256.IsHardwareAccelerated)
         {
@@ -22,7 +22,7 @@ internal class Av1DctDct4Forward2dTransformer : Av1Forward2dTransformerBase
         }
         else*/
         {
-            Transform2dCore(this.transformer, this.transformer, ref input, 4, ref output, this.config, ref this.temp[0], 8);
+            Transform2dCore(this.transformer, this.transformer, input, 4, output, this.config, this.temp, 8);
         }
     }
 
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Forward2dTransformerBase.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Forward2dTransformerBase.cs
index cb8e98fc70..dbe93cf8e3 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Forward2dTransformerBase.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Forward2dTransformerBase.cs
@@ -13,7 +13,7 @@ internal abstract class Av1Forward2dTransformerBase
     /// <summary>
     /// SVT: av1_tranform_two_d_core_c
     /// </summary>
-    protected static void Transform2dCore<TColumn, TRow>(TColumn transformFunctionColumn, TRow transformFunctionRow, ref short input, uint inputStride, ref int output, Av1Transform2dFlipConfiguration config, ref int buf, int bitDepth)
+    protected static void Transform2dCore<TColumn, TRow>(TColumn transformFunctionColumn, TRow transformFunctionRow, Span<short> input, uint inputStride, Span<int> output, Av1Transform2dFlipConfiguration config, Span<int> buf, int bitDepth)
             where TColumn : IAv1Forward1dTransformer
             where TRow : IAv1Forward1dTransformer
     {
@@ -45,8 +45,13 @@ internal abstract class Av1Forward2dTransformerBase
         // ASSERT(txfm_func_col != NULL);
         // ASSERT(txfm_func_row != NULL);
         // use output buffer as temp buffer
-        ref int tempIn = ref output;
-        ref int tempOut = ref Unsafe.Add(ref output, transformRowCount);
+        ref short inputRef = ref input[0];
+        ref int outputRef = ref output[0];
+        ref int bufRef = ref buf[0];
+        Span<int> tempInSpan = output.Slice(0, transformRowCount);
+        Span<int> tempOutSpan = output.Slice(transformRowCount, transformRowCount);
+        ref int tempIn = ref tempInSpan[0];
+        ref int tempOut = ref tempOutSpan[0];
 
         // Columns
         for (c = 0; c < transformColumnCount; ++c)
@@ -56,7 +61,7 @@ internal abstract class Av1Forward2dTransformerBase
                 uint t = (uint)c;
                 for (r = 0; r < transformRowCount; ++r)
                 {
-                    Unsafe.Add(ref tempIn, r) = Unsafe.Add(ref input, t);
+                    Unsafe.Add(ref tempIn, r) = Unsafe.Add(ref inputRef, t);
                     t += inputStride;
                 }
             }
@@ -66,20 +71,20 @@ internal abstract class Av1Forward2dTransformerBase
                 for (r = 0; r < transformRowCount; ++r)
                 {
                     // flip upside down
-                    Unsafe.Add(ref tempIn, r) = Unsafe.Add(ref input, t);
+                    Unsafe.Add(ref tempIn, r) = Unsafe.Add(ref inputRef, t);
                     t -= inputStride;
                 }
             }
 
             RoundShiftArray(ref tempIn, transformRowCount, -shift[0]); // NM svt_av1_round_shift_array_c
-            transformFunctionColumn.Transform(ref tempIn, ref tempOut, cosBitColumn, stageRangeColumn);
+            transformFunctionColumn.Transform(tempInSpan, tempOutSpan, cosBitColumn, stageRangeColumn);
             RoundShiftArray(ref tempOut, transformRowCount, -shift[1]); // NM svt_av1_round_shift_array_c
             if (!config.FlipLeftToRight)
             {
                 int t = c;
                 for (r = 0; r < transformRowCount; ++r)
                 {
-                    Unsafe.Add(ref buf, t) = Unsafe.Add(ref tempOut, r);
+                    Unsafe.Add(ref bufRef, t) = Unsafe.Add(ref tempOut, r);
                     t += transformColumnCount;
                 }
             }
@@ -89,7 +94,7 @@ internal abstract class Av1Forward2dTransformerBase
                 for (r = 0; r < transformRowCount; ++r)
                 {
                     // flip from left to right
-                    Unsafe.Add(ref buf, t) = Unsafe.Add(ref tempOut, r);
+                    Unsafe.Add(ref bufRef, t) = Unsafe.Add(ref tempOut, r);
                     t += transformColumnCount;
                 }
             }
@@ -98,8 +103,8 @@ internal abstract class Av1Forward2dTransformerBase
         // Rows
         for (r = 0; r < transformRowCount; ++r)
         {
-            transformFunctionRow.Transform(ref Unsafe.Add(ref buf, r * transformColumnCount), ref Unsafe.Add(ref output, r * transformColumnCount), cosBitRow, stageRangeRow);
-            RoundShiftArray(ref Unsafe.Add(ref output, r * transformColumnCount), transformColumnCount, -shift[2]);
+            transformFunctionRow.Transform(buf.Slice(r * transformColumnCount, transformColumnCount), output.Slice(r * transformColumnCount, transformColumnCount), cosBitRow, stageRangeRow);
+            RoundShiftArray(ref Unsafe.Add(ref outputRef, r * transformColumnCount), transformColumnCount, -shift[2]);
 
             if (Math.Abs(rectangleType) == 1)
             {
@@ -107,7 +112,7 @@ internal abstract class Av1Forward2dTransformerBase
                 // size difference is a factor of 2.
                 for (c = 0; c < transformColumnCount; ++c)
                 {
-                    ref int current = ref Unsafe.Add(ref output, (r * transformColumnCount) + c);
+                    ref int current = ref Unsafe.Add(ref outputRef, (r * transformColumnCount) + c);
                     current = Av1Math.RoundShift((long)current * NewSqrt2, NewSqrt2BitCount);
                 }
             }
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity16Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity16Forward1dTransformer.cs
index 3dc8be853f..78ab05d150 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity16Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity16Forward1dTransformer.cs
@@ -9,8 +9,12 @@ internal class Av1Identity16Forward1dTransformer : IAv1Forward1dTransformer
 {
     private const int TwiceNewSqrt2 = 2 * 5793;
 
-    public void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange)
-        => TransformScalar(ref input, ref output);
+    public void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange)
+    {
+        Guard.MustBeSizedAtLeast(input, 16, nameof(input));
+        Guard.MustBeSizedAtLeast(output, 16, nameof(output));
+        TransformScalar(ref input[0], ref output[0]);
+    }
 
     private static void TransformScalar(ref int input, ref int output)
     {
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity32Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity32Forward1dTransformer.cs
index 34985e9a9b..13ee029464 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity32Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity32Forward1dTransformer.cs
@@ -7,12 +7,16 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Transform.Forward;
 
 internal class Av1Identity32Forward1dTransformer : IAv1Forward1dTransformer
 {
-    public void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange)
+    public void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange)
     {
-        TransformScalar(ref input, ref output);
-        TransformScalar(ref Unsafe.Add(ref input, 8), ref Unsafe.Add(ref output, 8));
-        TransformScalar(ref Unsafe.Add(ref input, 16), ref Unsafe.Add(ref output, 16));
-        TransformScalar(ref Unsafe.Add(ref input, 24), ref Unsafe.Add(ref output, 24));
+        Guard.MustBeSizedAtLeast(input, 32, nameof(input));
+        Guard.MustBeSizedAtLeast(output, 32, nameof(output));
+        ref int inputRef = ref input[0];
+        ref int outputRef = ref output[0];
+        TransformScalar(ref inputRef, ref outputRef);
+        TransformScalar(ref Unsafe.Add(ref inputRef, 8), ref Unsafe.Add(ref outputRef, 8));
+        TransformScalar(ref Unsafe.Add(ref inputRef, 16), ref Unsafe.Add(ref outputRef, 16));
+        TransformScalar(ref Unsafe.Add(ref inputRef, 24), ref Unsafe.Add(ref outputRef, 24));
     }
 
     private static void TransformScalar(ref int input, ref int output)
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity4Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity4Forward1dTransformer.cs
index baa622b0a8..45a8a78fb1 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity4Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity4Forward1dTransformer.cs
@@ -7,8 +7,12 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Transform.Forward;
 
 internal class Av1Identity4Forward1dTransformer : IAv1Forward1dTransformer
 {
-    public void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange)
-        => TransformScalar(ref input, ref output);
+    public void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange)
+    {
+        Guard.MustBeSizedAtLeast(input, 4, nameof(input));
+        Guard.MustBeSizedAtLeast(output, 4, nameof(output));
+        TransformScalar(ref input[0], ref output[0]);
+    }
 
     private static void TransformScalar(ref int input, ref int output)
     {
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity64Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity64Forward1dTransformer.cs
index 2c3a351813..15a9ae658f 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity64Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity64Forward1dTransformer.cs
@@ -9,12 +9,16 @@ internal class Av1Identity64Forward1dTransformer : IAv1Forward1dTransformer
 {
     private const int QuadNewSqrt2 = 4 * 5793;
 
-    public void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange)
+    public void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange)
     {
-        TransformScalar(ref input, ref output);
-        TransformScalar(ref Unsafe.Add(ref input, 16), ref Unsafe.Add(ref output, 16));
-        TransformScalar(ref Unsafe.Add(ref input, 32), ref Unsafe.Add(ref output, 32));
-        TransformScalar(ref Unsafe.Add(ref input, 48), ref Unsafe.Add(ref output, 48));
+        Guard.MustBeSizedAtLeast(input, 64, nameof(input));
+        Guard.MustBeSizedAtLeast(output, 64, nameof(output));
+        ref int inputRef = ref input[0];
+        ref int outputRef = ref output[0];
+        TransformScalar(ref inputRef, ref outputRef);
+        TransformScalar(ref Unsafe.Add(ref inputRef, 16), ref Unsafe.Add(ref outputRef, 16));
+        TransformScalar(ref Unsafe.Add(ref inputRef, 32), ref Unsafe.Add(ref outputRef, 32));
+        TransformScalar(ref Unsafe.Add(ref inputRef, 48), ref Unsafe.Add(ref outputRef, 48));
     }
 
     private static void TransformScalar(ref int input, ref int output)
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity8Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity8Forward1dTransformer.cs
index 88c3585c0d..822e7b4ae6 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity8Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Forward/Av1Identity8Forward1dTransformer.cs
@@ -7,8 +7,12 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Transform.Forward;
 
 internal class Av1Identity8Forward1dTransformer : IAv1Forward1dTransformer
 {
-    public void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange)
-        => TransformScalar(ref input, ref output);
+    public void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange)
+    {
+        Guard.MustBeSizedAtLeast(input, 8, nameof(input));
+        Guard.MustBeSizedAtLeast(output, 8, nameof(output));
+        TransformScalar(ref input[0], ref output[0]);
+    }
 
     private static void TransformScalar(ref int input, ref int output)
     {
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/IAv1Forward1dTransformer.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/IAv1Forward1dTransformer.cs
index 4f58d0eafc..c77e27acee 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/IAv1Forward1dTransformer.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/IAv1Forward1dTransformer.cs
@@ -15,5 +15,5 @@ internal interface IAv1Forward1dTransformer
     /// <param name="output">Output coefficients.</param>
     /// <param name="cosBit">The cosinus bit.</param>
     /// <param name="stageRange">Stage ranges.</param>
-    void Transform(ref int input, ref int output, int cosBit, Span<byte> stageRange);
+    void Transform(Span<int> input, Span<int> output, int cosBit, Span<byte> stageRange);
 }
diff --git a/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1ForwardTransformTests.cs b/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1ForwardTransformTests.cs
index c9674cd442..484dc102c1 100644
--- a/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1ForwardTransformTests.cs
+++ b/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1ForwardTransformTests.cs
@@ -8,7 +8,8 @@ using SixLabors.ImageSharp.Formats.Heif.Av1.Transform.Forward;
 namespace SixLabors.ImageSharp.Tests.Formats.Heif.Av1;
 
 /// <summary>
-/// SVY: test/FwdTxfm2dTest.cc
+/// SVY: test/FwdTxfm1dTest.cc
+/// SVY: test/FwdTxfm2dAsmTest.cc
 /// </summary>
 [Trait("Format", "Avif")]
 public class Av1ForwardTransformTests
@@ -256,8 +257,8 @@ public class Av1ForwardTransformTests
 
             // calculate in forward transform functions
             transformerUnderTest.Transform(
-                ref inputOfTest[0],
-                ref outputOfTest[0],
+                inputOfTest,
+                outputOfTest,
                 config.CosBitColumn,
                 config.StageRangeColumn);